Fig. 11

Illustration of the hypothesized lactose intolerance relationship and the observed microbiome signature in macaques with diarrhea. Due to malabsorption of lactose in the small intestine water is trapped, subsequently the lactose enters the large intestine to primarily be fermented by lactobacilli. Consequently, the abundance of lactobacilli increases by the excess of substrate. The lactobacilli ferment the lactose into short chain fatty acids (SCFA) resulting in elevated concentrations of lactate, succinate in the lumen. The increased concentration of lactate and succinate leads to proliferations of lactate- and succinate-consuming bacteria. Water is attracted by the lumen of the intestine due to the osmotic effect of the increased SCFAs concentration, together with the earlier trapped water in the intestine resulting in osmotic diarrhea